8. The alignment material composition of claim 1, wherein a content of the
alignment material is 2 to 7 wt %, a content of the ultraviolet absorbent
is 0.2 to 2.0 wt %, and a content of the light stabilizer is 0.2 to 2.0
wt %.

9. An alignment layer, suitable for being used in a liquid crystal display
panel, constituents of the alignment layer comprising an alignment
material, an ultraviolet absorbent and a light stabilizer, wherein the
ultraviolet absorbent comprises a following formula 1-1 or a following
formula 1-2: ##STR00036## wherein X represents hydrogen, alkyl group or
halogen, and R1 represents benzene ring carbon long-chain derivative;the
light stabilizer comprising a following formula 2: ##STR00037## wherein
R2 represents ester-based derivative or amine-based derivative, and R3
represents hydrogen, hydroxyl group or alkyl group.

10. The alignment layer of claim 9, wherein absorption wavelengths of the
ultraviolet absorbent are wavelengths of ultraviolet light from 190 nm to
400 nm.

11. The alignment layer of claim 9, wherein the R1 of the ultraviolet
absorbent represents a substituted group shown as a following formula 3:
##STR00038## wherein A1 represents hydrogen, alkyl group or ##STR00039##
and A2 represents alkyl group, --CH2CH2CO(OCH2CH2)6,
--CH2CH2CO(OCH2CH2)7, ##STR00040##

12. The alignment layer of claim 11, wherein the ultraviolet absorbent is
selected from at least one of following compounds: ##STR00041##
##STR00042##

13. The alignment layer of claim 9, wherein the light stabilizer is
selected from at least one of following compounds: ##STR00043##
##STR00044##

15. The alignment layer of claim 9, wherein a weight ratio of the
alignment material to the ultraviolet absorbent to the light stabilizer
is 2-7:0.2-2.0:0.2-2.0.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001]This application claims the priority benefit of Taiwan application
serial no. 98106178, filed on Feb. 26, 2009. The entirety of the
above-mentioned patent application is hereby incorporated by reference
herein and made a part of specification.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to an alignment material composition
and an alignment layer, and particularly to an alignment material
composition and an alignment layer which effectively absorb ultraviolet
light and prevent aging of liquid crystals.

[0004]2. Description of Related Art

[0005]Recently, in order to make liquid crystal display (LCD) panels
achieve power conservation and lower power consumption, the industry
mostly sets driving devices at functions of lower frame frequencies and
grayscale display. However, since the charged ions existing in the LCD
panel have enough moving time to form an internal electrical field, the
internal electrical fields makes arranging directions of liquid crystals
change, thereby causing problems of display quality in the LCD panel. The
problems include: voltage holding ratios (VHR), threshold voltage,
flicker and image-retention effect, etc.

[0006]Reasons of forming above-mentioned charged ions often come from
materials of the liquid crystals or of an alignment layer, especially
when the liquid crystals or the alignment layer is irradiated by
ultraviolet light. Energy of ultraviolet light causes photo-chemical
reactions to occur within the liquid crystals or within the alignment
layer, and the charged ions are released. Therefore, when the LCD panel
is chronically irradiated by a backlight source or an external light
source, the above-mentioned problems will be gradually generated, and
this is conventionally known as the aging of liquid crystal.

SUMMARY OF THE INVENTION

[0007]In light of the above, the present invention provides an alignment
material composition and an alignment layer that effectively absorb
ultraviolet light and prevent the aging of liquid crystals.

[0008]The present invention provides an alignment material composition
which includes an alignment material, an ultraviolet absorbent, a light
stabilizer and a solvent. The ultraviolet absorbent has a following
formula 1-1 or a formula 1-2:

[0012]The present invention provides an alignment layer suitable to be
used in an LCD panel. Constituents of the alignment layer include the
above-mentioned alignment material, the ultraviolet absorbent and the
light stabilizer.

[0013]Due to the above, the alignment material composition and the
alignment layer of the present invention achieves effects of effectively
absorbing ultraviolet light and preventing aging of the liquid crystal
through adjusting categories and composition ratios of the alignment
material, the ultraviolet absorbent, the light stabilizer and the
solvent.

[0014]In order to make the aforementioned and other objects, features and
advantages of the present invention more comprehensible, several
embodiments accompanied with figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and constitute a
part of this specification. The drawings illustrate embodiments of the
invention and, together with the description, serve to explain the
principles of the invention.

[0016]FIG. 1 is a schematic view of an LCD panel.

[0017]FIG. 2 is a bar graph of voltage holding ratios under different
testing conditions according to different embodiments.

DESCRIPTION OF EMBODIMENTS

Alignment Material Composition

[0018]An alignment material composition of the present invention includes
an alignment material, an ultraviolet absorbent, a light stabilizer and a
solvent. The ultraviolet absorbent has a following formula 1-1 or a
formula 1-2:

[0022]In detail, the above alignment material includes, for example,
polyamide acid composition, but the present invention is not limited
thereto. R1 of the ultraviolet absorbent represents a substituted group
shown as following formula 3:

[0024]The above ultraviolet absorbent absorbs energy of ultraviolet light,
and especially according to an embodiment of the present invention, the
ultraviolet absorbent absorbs ultraviolet light having wavelengths
distributed from 190 nm to 400 nm. When the ultraviolet absorbent absorbs
ultraviolet light having wavelengths distributed from 190 nm to 400 nm,
energy of visible light having wavelengths from 400 nm to 720 nm is not
absorbed so that the brightness is not reduced. In other words,
transmittance of visible light is not reduced when preventing aging of
the liquid crystals.

[0025]For example, the above ultraviolet absorbent may be chosen from at
least one of following compounds:

[0034]The above ultraviolet absorbent has a chromophore group which
absorbs ultraviolet light having wavelengths from 190 nm to 400 nm in the
alignment material composition, the chromophore is, for example:
[0035]--N═N--; [0036]>C═N--; [0037]C--O; and [0038]--N═O.

[0039]Hence, the ultraviolet absorbent forms hydrogen bonds after
absorbing energy of ultraviolet light, and reversible reactions of
tautomerism between molecules occur to convert light energy into heat.
The ultraviolet absorbent returns to an original ground state after
depleting absorbed energy as heat.

[0040]In the alignment material composition provided by the present
invention, the above light stabilizer may be chosen from at least one of
following compounds:

##STR00019## ##STR00020##

[0041]A functioning mechanism of the above light stabilizer is that the
nitrogen atoms on a piperidine capture the peroxide radicals, so that the
peroxide radical enter a reversible reaction and cannot further damage
molecular bonds of the alignment material or liquid crystal material.

[0042]In addition, the above solvent may include:

N-Methyl Pyrrolidone (NMP)

##STR00021##

[0043]γ-Butyrolactone

##STR00022##

[0044]Ethylene Glycol Monobutyl Ether

##STR00023##

[0046]It should be noted that the alignment material composition provided
by the present invention has a characteristic of simultaneously adding
the ultraviolet absorbent and the light stabilizer into the alignment
material. In addition to protecting the alignment material, the
ultraviolet absorbent also protects the light stabilizer from being
damaged by ultraviolet light, thereby retaining original stabilizing
effects thereof. Hence, a synergistic effect on the aim of preventing
aging of the liquid crystal is achieved.

[0047]Although the above ultraviolet absorbent and the light stabilizer
both have functions of protecting the liquid crystal, functions thereof
are affected by a plurality of factors, for example: solubility,
dispersibility, volatility and molecular structure, and the like. In
addition, formability into a film when subsequently forming the alignment
layer needs to be taken into consideration in formation of the above
alignment material composition.

[0048]Considering each of the above factors, according to a preferred
embodiment of the present invention, in the above alignment material
composition, a content of the alignment material is 2 to 7 wt %, a
content of the ultraviolet absorbent is 0.2 to 2.0 wt %, and a content of
the light stabilizer is 0.2 to 2.0 wt %. The alignment material
composition having the above ranges obtains more obvious effects of
absorbing ultraviolet light and preventing the aging of the liquid
crystals.

Alignment Layer

[0049]FIG. 1 is a schematic view of an LCD panel. Referring to FIG. 1, the
present invention provides alignment layers 230a and 230b which are
suitable to be used in an LCD panel 200. Constituents of the alignment
layers 230a and 230b include the alignment material, the ultraviolet
absorbent and the light stabilizer. The formulas of the alignment
material, the ultraviolet absorbent and the light stabilizer have already
been illustrated in the above embodiments and are not repeatedly
illustrated here.

[0050]In the LCD panel 200, the alignment layers 230a and 230b are
respectively disposed on two substrates 210 and 220. The substrates 210
and 220 are, for example, a thin film transistor array substrate and a
color filter substrate, and a liquid crystal layer 240 is disposed
between the two alignment layers 230a and 230b. Constituents of the
alignment layers 230a and 230b are substantially the same as the
constituents of the alignment material composition according to the above
embodiments. A main difference is that in the constituents of the
alignment layers 230a and 230b, the solvent has been removed. In
practice, when producing the alignment layers 230a and 230b, a pre-baking
(at 120 degrees centigrade, 2 minutes) and a hard-baking (220 degrees
centigrade, 15 minutes) processes may be performed on the above alignment
material composition. Said process removes the solvent to obtain the
alignment layers 230a and 230b.

[0051]Since the alignment layers 230a and 230b provided by the present
invention have a synergistic effect by the ultraviolet absorbent and the
light stabilizer, there is a more significant effect of absorbing
ultraviolet light, and the aging of the liquid crystal layer 240 caused
by ultraviolet light when the LCD panel 200 is irradiated by a light L is
effectively prevented.

Voltage Holding Ratio

[0052]It should be noted that, in order to quantitatively analyze the
phenomenon of the aging of the liquid crystals, measurement of voltage
holding ratios are generally performed. To the above LCD panel 200, the
voltage holding ratio is an important parameter. The higher the voltage
holding ratio, the more aligned on a specific direction liquid crystal
molecules (not shown) in the liquid crystal layer 240 are maintained,
meaning that the LCD panel has a better display uniformity. However, when
the LCD panel is used under a lower driving frequency, the charged ions
(not shown) in the LCD panel 200 would have enough time to drift to the
interfaces 235a and 235b that are between the alignment layers 230a and
230b and the liquid crystal layer 240, so that the voltage holding ratio
of the liquid crystal layer 240 decreases. Hence, measuring the voltage
holding ratios under different driving frequencies may be designed, and
degrees of aging are known by comparing the results of measurement.

[0053]The following uses the voltage holding ratios of two embodiments to
illustrate the present invention.

Control Embodiment

[0054]According to the control embodiment of the present invention, a
material of the alignment layers is 100 grams of polyamide acid
compounds. Especially, no ultraviolet absorbents or light stabilizers is
added in the alignment layer. Testing of the voltage holding ratios is
performed on a sample produced according to said composition under
different driving frequencies and voltages, and a result is shown as S1
in FIG. 2. A testing condition A is a 60 hertz driving frequency and a 1
volt voltage; a testing condition B is a 0.6 hertz driving frequency and
a 1 volt voltage; a testing condition C is a 60 hertz driving frequency
and a 5 volt voltage; a testing condition D is a 0.6 hertz driving
frequency and a 5 volt voltage. In addition, in the above four testing
conditions, a scanning time of a frame is 60 microseconds.

[0055]Next, ultraviolet irradiation is performed on the sample according
to the present embodiment. After irradiating using energy of 50 mW per
second for 30 seconds, testing of the voltage holding ratios is performed
on the sample irradiated by ultraviolet light in the same measure
according to the above four testing conditions A, B, C and D. A result
thereof is shown as S2 in FIG. 2.

[0056]Referring to FIG. 2, after being irradiated by ultraviolet light,
the voltage holding ratios of the sample according to the present
embodiment are all lower than that before being irradiated by ultraviolet
light. Under testing conditions A and B, the voltage holding ratios are
both lower than 80%. Especially, the voltage holding ratio of the testing
condition B is even lower than 60%.

Most Preferred Embodiment

[0057]According to the most preferred embodiment of the present invention,
the weight of the material of the alignment layers is 99.6 grams, and the
alignment material includes polyamide acid composition and the solvent.
The ultraviolet absorbent is 0.2 gram of
(Phenol,2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)-).

##STR00024##

[0058]The light stabilizer is 0.2 gram, and the light stabilizer includes
following two compounds:

##STR00025##

[0059]According to the present embodiment, after a drying process, a
weight ratio of remaining solid content of the alignment material, the
ultraviolet absorbent and the light stabilizer of the alignment layers
230a and 230b is approximately 30:1:1.

[0060]Ultraviolet irradiation is performed on a sample produced according
to the above ratio. After irradiating with ultraviolet light having
energy of 50 mW per second for 30 seconds, measurement of the voltage
holding ratios is similarly performed according to the above four testing
conditions A, B, C and D. A result thereof is shown as S3 in FIG. 2.

[0061]Referring to FIG. 2, relative to the results according to the
control embodiment, even under the strictest testing condition B (low
driving frequency and low voltage), the voltage holding ratio according
to the present embodiment is still maintained above 70%, and is even
maintained above 94% under the other testing conditions A, C and D. In
addition, if only the ultraviolet absorbent is added in the alignment
material which is polyamide acid composition, the voltage holding ratio
under the testing condition B is approximately 62%. If only the light
stabilizer is added in the alignment material which is polyamide acid
composition, the voltage holding ratio under the testing condition B is
approximately 56% Hence, according to the present embodiment, the voltage
holding ratios of the alignment layer having both the above ultraviolet
absorbent and the light stabilizer are above 70%. The voltage holding
ratios are significantly enhanced compared with 62% when only the
ultraviolet absorbent is added or 56% when only the light stabilizer is
added.

[0062]In summary, since the ultraviolet absorbent and the light stabilizer
are both added into the alignment material of the alignment material
composition and the alignment layer of the present invention, the present
invention effectively prevents aging of the liquid crystals, maintains
uniformity and display effects, and increases a lifespan of the LCD
panel.

[0063]It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the present
invention without departing from the scope or spirit of the invention. In
view of the foregoing, it is intended that the present invention cover
modifications and variations of this invention provided they fall within
the scope of the following claims and their equivalents.